TWI416454B - A method for compensating the uniformity of a liquid crystal display with a non - uniform backlight and the display - Google Patents

Abstract

The invention relates to a method for compensating for poor uniformity of a liquid crystal display having a non-uniform backlight. By virtue of selecting a standard color that all cells can achieve to serve as a virtually primary color, the invention measures to give the relationship between the tri-stimulus values of the virtually primary color and those presented by the respective cells and records the resultant values to serve as compensation data. During operation of a display, the input image data are computed based on the compensation data for respective cells in accordance with the cell locations and converted into compensated image signals. As such, all of the cells are able to present the same chromaticity and brightness upon receiving the same image signal, thereby performing uniform chromaticity and brightness across the entire display.

Description

Method for compensating uniformity of liquid crystal display with non-uniform backlight and the display

The invention relates to a display uniformity compensation method, in particular to a non-uniform backlight liquid crystal display uniformity compensation method and the display.

The liquid crystal display mainly comprises a backlight panel at the rear and a liquid crystal module in front. Since the image display of the liquid crystal display uses a backlight in the backlight to illuminate the front color filter, the liquid crystal filter corresponds to the front liquid crystal mode. The primary color of red, green and blue is formed at each liquid crystal valve position; the electric signal is used to control the voltage between the electrodes on the front and rear sides of each liquid crystal valve. The light transmittance of the liquid crystal is small. For convenience of explanation, each liquid crystal valve is referred to herein as a sub-cell, and the red, green, and blue light respectively passing through the three sub-cells are mixed into one so-called A color pixel that combines the brightness and chromaticity that can be transmitted through each pixel position to form a full picture.

Since the color of the color-filter is made by the principle of dye translucency, the transmission spectrum T(λ) of the three basic colors of red, green and blue is as shown in Fig. 1. It shows that it has good reproducibility, so that the whole filter has a uniform light transmission. The R is the red basic light transmission spectrum, the G is the green light transmission spectrum, and the B is the blue light transmission spectrum. Because the LCD uses three basic colors of red, green, and blue color-filters to form pixels of various colors at each cell position, the backlight must use white light.

On the other hand, due to the development of the local color dimming control technology, in recent years, the three basic colors of the backlight panel can also have different brightness variations with the screen color. Due to the improved luminous efficiency of the LED and the cost reduction, and the LED For backlights, regional brightness control can be used to increase the contrast ratio. RGB LEDs can be used to increase the color gamut range beyond the NTSC standard, reducing the blurring effect (Moving Blur), reducing power consumption and ultra-thin The thickness of the design, as well as the absence of environmental pollution and many other benefits. Therefore, the use of LED as a backlight for LCD displays has been widely recognized and accepted by the market.

The use of LEDs as a light source can be divided into two methods, one is to use a blue LED to excite the fluorescent powder and emit a longer wavelength component to synthesize a white light white LED; the other method is to directly use RGB three color LED wafer combination to form white light. LED. However, regardless of the white light produced by the above, there is a problem of unevenness in chromaticity and brightness among the different LEDs. For example, when a blue LED die is used to excite fluorescent powder into white light, the wavelength of the blue light and the composition, proportion, and mixing state of the fluorescent powder affect the chromaticity and brightness of the white light, so that the same type of product White LEDs are more yellowish, and some are more bluish; if they are classified by their color coordinates, the range is about 0.26~0.36.

Similarly, when white light is synthesized by RGB three-color LED crystal grains, the color coordinates of the white light mixed by each unit cell are different due to the different color coordinates of the basic colors of the respective crystal grains. Although the applicant has the Republic of China Announcement No. 480879 "Method for Compensating the Color Unevenness of Color Display", it has been revealed that when RGB three-color LEDs are used as white light sources, individual RGB can be adjusted to different brightness distributions. The synthesized light is similar in chromaticity and brightness at each pixel.

In view of the above, since the chromaticity and brightness of the respective light sources are still different, even if the backlight passes through the diffuser, it may not be able to provide uniform illumination of the full picture. If the main backlight of the i-th unit cell in the liquid crystal module is LEDi, and the main backlight of the i+1th cell is LEDi+1. When the LEDi illuminating component is more reddish, and LEDi+1 is more blue, and for convenience of explanation, the image signal intensity is set to be between 0 and 1, where 0 means that the light valve is fully closed, and 1 means that the light valve is fully open. When the full white screen needs to be displayed, the image signals (S _r , S _g , S _b ) _i provided to each unit cell are all (1.0, 1.0, 1.0), indicating three sub-cells of red, green and blue. The light valves are all fully open. Since the LEDi is reddish, the pixel i displayed by the cell position will also be reddish, and the LEDi+1 will be blue, so the pixel i+1 will also be bluish, so the chromaticity and brightness of the entire picture will be uneven.

In particular, in accordance with current practice, in order to reduce the cost and structural cost of the LED driving circuit, a common circuit is shown in FIG. 2, and a plurality of LEDs are driven in series at a driving voltage V _DD greater than the total forward bias of all series LEDs. Fluorescent white LED or RGB LED). In this example, the driving current Is is a constant current source, and a set of control circuits adjusts the duty-cycle ratio of the constant current source between 0 and 1 to output different sizes. A PWM (pulse-width modulation) signal is used to synchronously enable the entire string of LEDs to illuminate, thereby adjusting the brightness of the string of LEDs.

However, in this driving mode, the effective luminous current of the entire string of LEDs can only be a single value between 0 and 1 s. Although the cost can be reduced, the chromaticity and brightness of the string of LEDs cannot be individually adjusted. Therefore, when the chromaticity and brightness of the individual LEDs in the string of LEDs are not uniform, the above-mentioned techniques possessed by the applicant cannot be used for compensation, resulting in uneven chromaticity and brightness of each pixel on the LCD display screen.

To improve the above unevenness, the only way to do this is to sort the chromaticity and brightness of all the LED dies one by one; especially the human eye has a good ability to distinguish between brightness and chromaticity, so that the average person can't visually Clearly distinguishing the level of brightness and chromaticity, the classification must be quite detailed: if the LED as a backlight is Using blue light to excite the phosphor powder structure, the chroma classification (bin) needs to be more than 20 kinds, and the brightness classification is more than 5 kinds, the two conditions are multiplied, the total classification number may reach 100; if it is red, green, The combination of blue three-color LED crystal grains constitutes a white light structure, and the chromaticity and brightness classification of each basic color need to be distinguished into about 30 kinds, and the total number of classifications obtained by adding three colors is also about 100 kinds.

When the classification of backlight crystals or unit cells is so numerous, whether it is the storage of raw materials or the management of incoming goods, it will cause significant troubles to the inventory. Relatively, the trouble of such procurement and management will also greatly increase the manufacturing cost in disguise, making the working hours unnecessary. Increasing, product prices are exploding; the more serious problem is that the brightness and chromaticity of each LCD display itself are uniform, but even if the two monitors of the same brand are juxtaposed in the store, it may still be The choice of backlight LEDs is different, so that the chromaticity and brightness of each other are different, which not only causes a major problem in quality control, but also causes consumers to doubt the quality of the product.

Therefore, the industry does not expect to have a proper solution, not only to ensure the brightness and chromaticity of the product itself, but also to ensure that each display has the same brightness and chromaticity; in particular, LED dies of different brightness and chromaticity can be used as the backlight source, without Close classification can increase manufacturing flexibility and reduce selection costs.

SUMMARY OF THE INVENTION One object of the present invention is to provide a method for compensating for uniformity of a liquid crystal display having a non-uniform backlight by ensuring brightness and chromaticity uniformity of the liquid crystal display itself.

Another object of the present invention is to provide a method for compensating for uniformity of a liquid crystal display having a non-uniform backlight panel, which can ensure that the brightness and chromaticity of each liquid crystal display product are maintained at the same level among all liquid crystal display products.

Still another object of the present invention is to provide a light source that can be greatly reduced as a backlight The number of classifications of LED dies, even without classification, thereby increasing the flexibility of selection of the liquid crystal display uniformity compensation method with non-uniform backlight.

Still another object of the present invention is to provide a liquid crystal display which can ensure uniform brightness and chromaticity of a rendered picture even if the brightness and chromaticity of the backlight used are not uniform.

Still another object of the present invention is to provide a liquid crystal display which can adopt a backlight panel which is uneven in brightness and chromaticity, and can still maintain uniform brightness and chromaticity of a product image, thereby increasing material selection flexibility and reducing production cost.

Therefore, the present invention discloses a uniformity compensation method for a liquid crystal display with a non-uniform backlight, wherein the liquid crystal display comprises a set of non-uniform backlights, and a group of cells on the light-emitting side of the backlight includes a plurality of cells with a changeable light transmittance. a liquid crystal module that displays a picture composed of a plurality of pixels and that is divided into a plurality of adjustment regions, a set of control devices for controlling individual light transmittance of each of the cells, and a set of stored plural a memory device for compensating data corresponding to the brightness and chromaticity distribution of each of the adjustment regions according to the brightness and chromaticity distribution of the adjustment regions, and the method comprises the following steps: a) receiving Image data from an image source, including a plurality of image signals for instructing the individual light transmittances of the cells, and b) the image signals in the image data according to the corresponding adjustment regions, according to the compensation Data weighting operation to obtain compensated image data including a plurality of compensated image signals respectively corresponding to each of the unit cells; and c) according to the compensated images Number, determines the cell rate of the individual light permeability of the liquid crystal module.

The liquid crystal display disclosed in the present disclosure comprises: a set of non-uniform backlights; a set of light-emitting sides of the backlight, including a plurality of cells having different light transmittances and having a plurality of cells, respectively, for displaying by a plurality of pixels a screen, and the unit cell is divided into a plurality of adjustment regions of the liquid crystal module; a group of stored in accordance with the backlight a memory device that illuminates the brightness and chromaticity distribution of the adjustment regions, and corresponding to the compensation data for uniformizing the transmission brightness and chromaticity distribution of each of the adjustment regions; and a set of individual light fluxes for controlling each of the above cells Transmitting and filtering the image signals from an image source, including image signals for instructing the individual light transmittances of all of the cells, according to the corresponding adjustment regions, and weighting the compensation data according to the compensation data Computing, determining a control device for the individual light transmittance of the cell in the liquid crystal module; causing one of the image signals to transmit light to any one of the cells corresponding to the image signal, At least one of the remaining cells in the unit cell is transmissive by the compensated image signal.

The present invention records the difference between the three-color stimulus value and the three-color stimulus value of the virtual basic color by defining a virtual basic color and measuring the difference between the three-color stimulation value and the virtual basic color after all the adjustment areas are affected by the rear uneven backlight. Then, when receiving the image data from the image source, the original image signal is converted into the compensation image signal according to the compensation data of each unit cell, which not only ensures the uniformity of brightness and chromaticity of the liquid crystal display itself, but further can further Ensure that the brightness and chromaticity of each LCD monitor product are maintained at the same level, and all product quality is neatly drawn; in particular, the number of classifications of LED dies as backlight sources can be greatly reduced, even without classification, thereby increasing material flexibility and reducing cost. .

Therefore, through the technology disclosed by the present invention, the liquid crystal display can ensure the uniformity of brightness and chromaticity of the presented picture even under the condition of uneven brightness and chromaticity of the used backlight board; Reduce production costs and provide more profitable LCD monitors.

The foregoing and other technical contents, features and effects of the present invention are as follows The detailed description of the preferred embodiments with reference to the drawings will be clearly understood. In the present case, the backlight board can be formed not only by a backlight composed of LED1, LED2, . . . , LEDn or the like, but also by a cold cathode tube (CCFL) and an LED. Moreover, the LEDs may be formed by LED modules composed of R, G, and B crystal grains, or white LEDs (for example, blue LED plus fluorescent powder mixed light), or white LEDs and RGB LEDs.

Since the three basic colors of each unit cell position are respectively controlled by the image signals (S _r , S _g , S _b ), the light transmittance of each unit cell is controlled by the brightness of each color of each unit cell. A point source consisting of three basic colors. As mentioned above, even if the filter can be regarded as uniform, due to the unevenness of the chromaticity and brightness of the backlight, the chromaticity and brightness of the three basic colors of red, green and blue appearing at the position of each unit cell are inevitable. not exactly. In addition, the light beams passed by the three sub-cells are not substantially pure colors. Therefore, the main basis of the present invention is to treat the three sub-cells of red, green and blue of each unit cell as three. An independent three primary color illumination source.

In order to make the chromaticity and brightness of each unit cell uniform, this case selects a "virtually primary color" as a standard according to the chromaticity and brightness that each unit cell can display in the display. And in units of unit cells, respectively change the input (S _r , S _g , S _b ) _{i of} the original image signal to (S _r ', S _g ', S _b ') _i , so that each unit cell is backlit After the source is irradiated, the red (R), green (G), and blue (B) three subunits at the unit cell position i after the beam of the red, green, and blue sub-cells are transparently added. The tri-stimulus value after the light-transparent color is matched with the three-color stimulus value of the "virtual basic color" on the color spectrum, so that the entire display screen can be evenly distributed, and even the entire product The line-output displays all have a uniform color and brightness.

Selecting a suitable "virtual basic color" step is shown in Figure 3. First, in step 31, the individual tristimulus values of the three sub-cells of each unit cell in the fully open state of the light valve are measured one by one. Here, the tristimulus values of the red sub-cells defining the i-th unit cell are (X _r , Y _r , Z _r ) _i , and the green sub-cells are transmitted through the three-color stimulus value. For (X _g , Y _g , Z _g ) _i , the three-color stimulus value of the blue sub-cell pass light transmission is (X _b , Y _b , Z _b ) _i ; and corresponding to the color coordinates on the color spectrum (x _r , y _r ) _i , (x _g , y _g ) _i , (x _b , y _b ) _i . In this example, as shown in FIGS. 4 and 5, the liquid crystal display has a plurality of direct-illuminated LEDs 41, 42... disposed on the substrate 4 as a backlight, and after passing through the filter 5, respectively, is irradiated to the liquid crystal. In the unit cell of the module 6, since the thickness of the backlight of the LCD TV is as thin as illustrated in this example, each of the cells 61, 62 is mainly irradiated only by a single LED 41, 42 and the respective unit cells are considered. The illumination angle of the LED in the backlight panel will be inversely proportional to the thickness ratio, and there may be a very large difference in chromaticity and brightness.

In step 32, the color coordinates of the subcells of all unit cell positions are respectively drawn in the color coordinates specified by CIE1931, as shown in Fig. 6, wherein the R region is the red subcell permeation of each unit cell. The color coordinate area of the light, the G area is the color coordinate area of all the green sub-cells, and the B area is the collection area of all the blue sub-cells. Of course, as can be easily understood by those skilled in the art, this step is mainly planned to facilitate understanding of the technology of the present invention. In actual sampling and calculation, the operation of the processor does not need to actually plot any coordinates into the color spectrum.

Then, in step 33, among the tristimulus values (X _r , Y _r , Z _r ) _i of all the red sub cells, a value equal to the smallest X _r value, or even less than the minimum X _r is selected. The stimulus value for the red virtual base color, ie X _rv (X _r ) _min ; and select a value equal to or greater than the maximum Y _r value as the stimulus value Y value of the red virtual basic color, ie Y _rv (Y _r ) _max , a value equal to or greater than the maximum Z _r value as the stimulus value Z value, ie Z _rv (Z _r ) _max .

Thereby, the color coordinates of the red virtual basic color are set , The coordinates are marked as point A as shown in Fig. 6. The color is the chromaticity of all the red sub-cells, and the farthest from the red solid color in the color spectrum, so that all the red sub-cells can achieve the color. The standard of coordinates.

Similarly, in all the green sub-cell tristimulus values (X _gi , Y _gi , Z _gi ), the Y _g value with the smallest green stimulus value or a smaller value is taken as the Y value of the green virtual basic color. Y _gv (Y _g ) _min , and the X value and the Z value of the green virtual basic color are equal to or greater than the maximum X _g value and the maximum Z _g value; that is, X _gv (X _g ) _max , Z _gv (Z _g ) _max ; Obtain the "green virtual basic color" color coordinates as shown by point B in the figure . Similarly, the blue virtual basic color Z _bv (Z _b ) _min , X _bv (X _b ) _max , Y _bv (Y _b ) _max , the color coordinates are , The color coordinates are marked as point C shown in the figure.

Of course, this virtual basic color is not the only solution. Others can form different virtual basic colors according to the above rules. Only the color coordinates of the three virtual basic colors are larger around the triangle area, and the more colors that can be presented. . The "virtual basic color" is the chromaticity that all the cells can exhibit under the condition that the display is matched with the backlight behind the liquid crystal module. That is, when the light transmittance of each unit cell is moderately adjusted, each unit cell of the display can exhibit the same chromaticity for any of the same original image signals (S _r , S _g , S _b ), so that The color of the picture display is uniform.

When the three-color stimulation value of the three sub-cells of any unit cell i (the value measured in the full-open state of the light valve) is adjusted to conform to the above-described virtual basic color, respectively (X _rv , Y _rv , Z _rv ), (X _gv , Y _gv , Z _gv ), (X _bv , Y _bv , Z _bv ), after the original image signal (S _r , S _g , S _b ) _{i is} input, the cell position i is actually displayed The tristimulus values (X _i , Y _i , Z _i ) of the pixel are:

However, when the photocell signal is fully open, the tristimulus values of the three basic colors measured are (X _r , Y _r , Z _r ) _i , (X _g , Y _g , Z _g ) _i , (X _b , Y _b , Z _b ) _i Therefore, the three-color stimulus value (X _i ') of the unit cell i when driven by the compensated image signal (S _r ', S _g ', S _b ') _i , Y _i ', Z _i ') are:

In other words, the original image signal (S _r , S _g , S _b ) _{i is} converted into a compensated video signal (S _r ', S _g ', S _b ') _i by the compensation data, and the compensated video signal is received (S _The tristimulus values (X _i ', Y _i ', Z _i ') of the pixels displayed by the unit cell position i of _r ', S _g ', S _b ') _i can conform to the "virtual basic color" as the three primary colors. After the liquid crystal display is driven by the original image signal (S _r , S _g , S _b ) _i , the tristimulus values (X _i , Y _i , Z _i ) should be presented.

Therefore, in step 34, the three color stimulating values of the three sub-cells of each unit cell of the measured display are respectively compared with the virtual basic color when the light valve is fully opened, and the weighting calculation is made to match The weight of the virtual basic color, that is, the (X _i ', Y _i ', Z _i ') chromaticity of the three-color stimulus value of the color image presented when the compensation image signal is actually applied to each unit cell The brightness can be the same as the stimulus value (X _i , Y _i , Z _i ) exhibited by the original image signal when the virtual basic color is the three primary colors. therefore: Simplified to M _i [S'] _i =M _v [S] _i ... (6) Therefore, [S'] _i =M _i ^-1 * M _v [S] _i ≡(M _T ) _i [S] _i .........(7)

When the image signal is within the virtual basic color range in the color spectrum, the compensated image signal (S _r ', S _g ', S _b ') after the (7) conversion must have a solution greater than zero. And any original image signal (S _r , S _g , S _b ) _i input to the position of the unit cell i, the image signal conversion compensation is performed by the equation (7), and the pixel chromaticity and brightness are output at the unit i position, which will be exactly Ideally, when the virtual basic color is the three primary colors and the original image signal is received, the pixel output is exactly the same. The entire picture has only one virtual base color as the reference, and the entire picture will exhibit the same uniform color and brightness. Similarly, if all products in the entire product line select the same virtual base color, each LCD of the product line has the same color and brightness.

Therefore, it can be seen from the equation (7) that the actual operation of the above step 34 is to perform a matrix operation of M _i ^-1 * M _v for each unit cell i after the LCD panel is manufactured. First, the inverse matrix M _i ^-1 of the three basic color tristimulus value matrix obtained by each cell position i in the fully open state of the light valve is obtained, and the one selected in the above step 33 is suitable as the virtual basic color. The matrix M _{v of the} tristimulus values is calculated by a computer to calculate the matrix of M _i ^-1 * M _v to obtain a 3x3 transformation matrix (M _T ) _i , and the transformation matrix (M _T ) _{i is} stored in an example. Released as a memory device for non-volatile memory (E2PROM).

In the case of an HDTV LCD TV, the total resolution is about 2 million pixels, that is, 2 million cells are formed in the structure, and each cell needs to store matrix data of 9 bytes. Therefore, the E2PROM requires approximately 18 Mbytes of storage space. Therefore, when the display is shipped from the factory, as shown in step 35, the display receives image data input by an image source and including a plurality of original image signals, and each image signal is used to instruct the corresponding light transmittance of the unit cell.

Then, in step 36, the image signals in the image data are respectively subjected to a real-time operation of the ASIC (Special Application IC) integrated circuit of the fast logical parallel operation of the hardware according to the corresponding adjustment region. The compensation data, which is exemplified by the conversion matrix (M _T ) _i of the formula (7), is applied to each of the original image signal weighting operations to obtain compensated image data including a plurality of compensated image signals respectively corresponding to each of the unit cells. Finally, the liquid crystal module determines the individual light transmittance of each unit cell according to the calculated compensated image signals (S _r ', S _g ', S _b ') in step 37. Therefore, any original image signal (S _r , S _g , S _b ) can be processed by the instant image to obtain and display the corresponding compensated image signal.

Since the compensated image signal is originally based on the chromaticity of each unit cell under the backlight corresponding to the back of the unit cell, the chromaticity can be considered, and the same chromaticity and brightness can be exhibited by each unit cell. The unified standard is used as the "virtual basic color". Therefore, after applying the compensation data, the original chromaticity unevenness of the liquid crystal display hardware is solved by the mutual compensation between the sub-cells. Therefore, after the correction data of the present case is corrected, even if the original image signal is a solid color such as pure red, (S _r , S _g , S _b ) _i = (1, 0, 0), the adjusted compensation image In the data, S _ri ' will be less than 1, and at least one of S _gi ' and S _bi ' is greater than 0 to compensate for the difference between the red sub-cell of the virtual basic color and the red sub-cell of the unit cell position i in the full opening of the light valve. The phenomenon has also become a special result in the actual implementation of the case.

Of course, as is well understood by those skilled in the art, according to the current technology, when a blue LED chip is used to excite the phosphor powder and the white light is used as a backlight, the biggest disadvantage is the red component in the white LED spectrum. It is obviously low, causing the color of the object to be irradiated to be blue and white, that is, the so-called pale feeling. The current solution is mainly to, for example, further reduce the transparency ratio of the green and blue components, so that the emitted light beam is again reddened in the color spectrum. However, this method undoubtedly causes the overall brightness of the illuminating beam to decrease, resulting in a problem of insufficient brightness; it is necessary to solve the problem of insufficient brightness, and it is necessary to increase the overall brightness of the backlight panel, which not only has technical limitations, but also increases The cost and manufacturing difficulty of electric current and heat dissipation structure.

As shown in FIG. 7, the second embodiment of the present invention uses a 42-inch LCD TV as an example. If 5 lm of white LEDs 41' and 42' are used in the backlight, a total of about 2,000 white LEDs are required. The coordinates are (0.28, 0.3), which is blue-white. If 200 red LEDs 40' of 2 lm are added, the composition of red light is relatively increased. Since the spectrum is just in the R region of the color filter transmission spectrum T(λ), as shown in FIG. 1, the highest light transmittance will increase the overall color coordinate Δx of the backlight panel to about 0.38. Thus the display will increase the red component.

However, only 200 red LEDs 40' are added. Compared with the huge area of the 42-inch display panel, the reinforcing red light must not be evenly distributed. Therefore, according to the above technique of the present invention, the unevenness caused by the red LED 40' is On the one hand, it can be compensated by changing the input image signal; and when the "virtual basic color" is selected, the reddish virtual three primary colors can be selected to move the chromaticity of the overall picture to the reddish direction of the color spectrum, Compensates for a white picture that is originally lacking red components. With this method, the display will not need to reduce the green and blue light transmittance of the filter 5' or reduce the liquid crystal. The green and blue subcell light transmittance of the module 6' sacrifices the overall brightness.

Furthermore, in the third embodiment of the present invention, as shown in FIG. 8, when the distance between the backlight substrate 4" and the filter 5" and the liquid crystal module 6" is large, the light beams of the plurality of LEDs will diffuse each other, so that the unit cell 61", 62" may be simultaneously illuminated by a plurality of LEDs 41", 42". For the sake of explanation, the R, G, and B subcells in the cell 61" are defined by the illumination factor λ _{1 of the} LED 41". The illumination factor λ _{2 of the} LED 42". If only LED 41" is illuminated (ie, λ ₁ =1, λ ₂ =0), the color coordinates of the R, G, and B sub-cells on the color spectrum are respectively recorded as (x _k1 , y _k1 ) (k = r, g, b), that is, the points 41 _r ', 41 _g ', 41 _b ' shown in Fig. 9; and only when the LED 42" is irradiated (ie, λ ₁ =0, λ ₂ =1), the R, G, B sub-crystal The color coordinates of the cells are labeled (x _k2 , y _k2 ) (k = r, g, b), that is, points 42 _r ', 42 _g ', 42 _b ' of Fig. 9. When LED 41" is illuminated by λ ₁ (0 λ ₁ 1), LED 42" with illumination coefficient λ ₂ (0 λ ₂ 1) When simultaneously irradiated, the color coordinates (x _km , y _km ) of the R, G, and B sub-cells after mixing are based on the color mixing principle.

It can be seen from equation (8) that the color coordinates after the light mixing are inevitably between the points 41 _r ', 41 _g ', 41 _b ' at the respective illuminations and the points 42 _r ', 42 _g ', 42 _b ' At a certain point between the lines, the ratio is weighted according to the spatial relationship between the LEDs 41", 42" and the unit cell 61".

When the above description is indicated by a numeral, only the LED 41" is irradiated (ie, λ ₁ =1, λ ₂ =0), and the sub-cells R, G, B of the unit cell i are compensated for the image signals S _r ', S _{When g} ', S _b ' is input, the three-color stimulus values X ₁ ', Y ₁ ', Z ₁ '

When only the LED 42" is illuminated (ie, λ ₁ =0, λ ₂ =1), each of the unit cells R, G, and B is input when compensating for the image signals S _r ', S _g ', S _b ' The three-color stimulus values of light transmission X ₂ ', Y ₂ ', Z ₂ ' are

Therefore, if the LED 41" and the LED 42" are simultaneously irradiated with the illumination coefficients λ ₁ and λ ₂ respectively, the combined light of the sub-cells R, G, B at the input of the compensated image signals S _r ', S _g ', S _b ' The tristimulus values X _T ', Y _T ', Z _T ' are

If the three-color stimulus value after the light mixing is required to be equal to the three-color stimulus value when the selected "virtual basic color" is the three primary colors and the original image signals S _r , S _g , and S _{b are} input, Its relationship becomes:

therefore

It can be seen from equation (10) that the compensated image signals (S _r ', S _g ', S _b ') can be calculated by matrix operations of M _v ^-1 M ₁ and M _v ^-1 M ₂ , and then weighting the illumination coefficient λ ₁ and λ ₂ are linearly operated and known by inverse matrix operations. The operations of M _v ^-1 M ₁ and M _v ^-1 M ₂ can be stored in the memory device by external computing into a 3 × 3 matrix. If the entire backlight panel consists of 1000 LEDs of different brightness and chromaticity, a total of 1000 M _i matrices and a M _v matrix of the selected "virtual basic color" are required, using M _v ^-1 M ₁ and M _v ^-1 The operation of M ₂ is stored in the E2PROM (the memory requires a memory space of 1001 × 9 words). For each unit cell i, several λ _k values that have a large influence on the pixel (larger illumination coefficient) must be memorized. For example, there may be four adjacent LEDs of the upper, lower, left and right sides. Larger impact, so if there are 2M cells in the panel, a total of 2M×16=32M word memory space needs to be stored. Using the above principle, the desired conversion signals (S _r ', S _g ', S _b ') _{i of} any unit cell _i can be expanded to:

Among them, LED _j , LED _j+1 , ..., LED _j+m represent m+1 LEDs which have a large influence on the cell i.

Therefore, if there are five LEDs that can affect a certain unit cell i, the red color that the unit cell i can display is also formed by the common light of five LEDs. The red light that the unit cell can present is after the light is mixed. The color coordinates will be as shown in Fig. 10, and it is also inevitable that some LEDs respectively illuminate the pentagon formed by the original color coordinates 41r", 42r", 43r", 44r", 45r" of the unit cell i. That is, no matter how many LEDs of the backlight board are composed and diffused by each other, the basic color coordinates of any unit cell in the entire panel must fall within the basic color area when the individual LEDs are illuminated, for example, in FIG. R area, Zone G, and Zone B. This also means that even if each unit cell is affected by the common light-mixing illumination of multiple LEDs in the backlight panel, a simple "virtual basic color" can be selected.

Furthermore, if the backlight panel uses local dimming control, the LED _{k of} each zone can be adjusted to its brightness level α _k (0 α _k 1), therefore, the tri-color stimulus value matrix M _{i of} the LED of the area can be written as α _k M _k , and when each LED _{k is} selected, the original image signal applied to each unit cell i must be converted into another compensated image signal. In order to maintain the ideal out of the image. According to the above, at this time, the formula (11) must be rewritten as:

By using equation (12), it is possible to simultaneously obtain compensated video signals (S _r ', S _g ', S _b ') of "area brightness control" with uniform chromaticity and brightness. It can be seen that the present invention can also solve the problem of mutual diffusion and chromaticity and brightness unevenness in the "area brightness control" interval. As can be seen from the above description, the present invention can indeed select a less saturated "virtual basic color" as a A standard color of a common target, and then use the image signal to drive the LCD. When the original image signal (S _r , S _g , S _b ) has only one of the color components (ie, only one of S _r , S _g , and S _b has a value greater than zero, the others are zero), then 7-1) After converting to a new image signal (S _r ', S _g ', S _b '), the three values S _r ', S _g ', S _b ' may have values greater than zero. That is to say, if the original image signal has only a red primary color, but it must be compensated for a less saturated "virtual basic color" of red, the green sub-pixel and the blue sub-pixel may also be lightly bright to form a less saturated Red basic color. However, because the color saturation of the LED is very high, the color range of the "less saturated""virtual basic color" selected is still quite large enough to constitute a high-quality color LCD panel.

Although the above embodiments use a direct-illuminated LED as a backlight, those skilled in the art can easily understand that the disclosed technology is not limited to the backlight of the direct-illuminated LED structure, as shown in FIG. In the fourth embodiment, even if the backlight comprises a light bar composed of side-emitting LEDs 41"', 42"', and is emitted by the LEDs 41"', 42"' by the light guide 43"' The beam steering filter 5"' enters the liquid crystal module 6"', and the above manner can still be applied to solve the problem of brightness and chromaticity unevenness of the pixels appearing in the position of each unit cell of the display.

Even, as shown in the fifth embodiment of FIG. 12, even if the cold cathode tubes 4 _L "" and _4R "" are used as the backlight, the chromaticity and brightness of the cold cathode tubes on both sides are limited, or the same. The non-uniformity of the cold cathode tube itself in the longitudinal direction can still be solved by implementing the technology of the present invention and adjusting the image signal of the actual input driving liquid crystal module.

However, the above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications according to the scope of the present invention and the description of the invention are all It is still within the scope of the invention patent.

4, 4" ‧ ‧ substrate

4 _L ””, 4 _R ””‧‧‧ Cold cathode tube

5, 5', 5", 5" ‧ ‧ ‧ filters

6,6', 6", 6"'‧‧‧ LCD Module

31~37‧‧‧Steps

43”’‧‧‧Light guide

41, 42, 40', 41', 42', 41", 42", 41"', 42" ‧ ‧ LED

41 _r ', 41 _g ', 41 _b ', 42 _r ', 42 _g ', 42 _b ', 41r", 42r", 43r", 44r", 45r", A, B, C‧‧

61, 62, 61", 62" ‧ ‧ unit cell

1 is a schematic diagram of a conventional filter transmittance versus wavelength change; FIG. 2 is a schematic diagram of a conventional light-emitting diode die drive circuit; FIG. 3 is a flow chart of the first preferred embodiment of the present invention; A perspective exploded view of a liquid crystal display of a first preferred embodiment; FIG. 5 is a schematic diagram showing the selection of a virtual basic color in a color spectrum of a pass beam of each unit cell in the embodiment of FIG. 4; FIG. 6 is a side view of the structure of the embodiment of FIG. 4. FIG. FIG. 8 is a side elevational view showing the structure of a third preferred embodiment of the present invention; FIG. 9 is a schematic view showing the structure of a unit cell of FIG. The coordinate diagram shows the weighted influence of two different light sources on the same unit cell; FIG. 10 is a schematic diagram of the color spectrum of the transparent beam of a unit cell in the embodiment of FIG. 8 when the plurality of light sources simultaneously act on a unit cell; FIG. 11 is a perspective exploded view of a liquid crystal display according to a fourth preferred embodiment of the present invention; and FIG. 12 is a perspective exploded view of a liquid crystal display according to a fifth preferred embodiment of the present invention.

31~37‧‧‧ Process steps

Claims (3)

A method for uniformity compensation of a liquid crystal display having a non-uniform backlight, wherein the liquid crystal display comprises a set of non-uniform backlights, a set of cells on the light exit side of the backlight, including a plurality of cells with a changeable light transmittance, for display by a plurality a pixel-constituting screen, and the unit cell is divided into a plurality of liquid crystal modules of the adjustment area, a set of control means for controlling the individual light transmittance of each of the cells, and a set of stored in accordance with the backlight The plate illuminates the brightness and chromaticity distribution of the adjustment regions, and corresponds to a memory device for compensating data for uniformizing the transmission brightness and chromaticity distribution of each of the adjustment regions, and the method comprises the following steps: a) obtaining the above compensation data The compensation data is used to adjust the illuminance chromaticity of the adjustment area to a virtual basic color, so that the brightness and chromaticity distribution of the adjustment area are uniformized; b) receiving from an image source, including a plurality of instructions for instructing all The image data of the image signal of the individual light transmittance of the unit cell; c) the image signals in the image data are respectively adjusted according to the corresponding And obtaining, according to the weighting operation of the compensation data, compensation image data including a plurality of compensated image signals corresponding to each of the unit cells; and d) determining, according to the compensated image signals, the unit cells in the liquid crystal module Light transmittance; wherein, the steps a) define the three basic color values of the red, green and blue basic colors of the virtual basic color are (X _rv , Y _rv , Z _rv ), (X _gv , Y _gb , Z _gv ), (X _bv , Y _bv , Z _bv ), and measuring one of the unit cells i, when the liquid crystal valve has the highest light transmittance, three basic colors of red, green and blue three-color stimulation The values are (X _r , Y _r , Z _r ) _i , (X _g , Y _g , Z _g ) _i , (X _b , Y _b , Z _b ) _i ; then the compensated image signal of the unit cell The relationship between S' _r , S' _g , S' _b ) and the image signal (S _r , S _g , S _b ) _i is: A method for uniformity compensation of a liquid crystal display having a non-uniform backlight, wherein the liquid crystal display comprises a set of non-uniform backlights, a set of cells on the light exit side of the backlight, including a plurality of cells with a changeable light transmittance, for display by a plurality a pixel-constituting screen, and the unit cell is divided into a plurality of liquid crystal modules of the adjustment area, a set of control means for controlling the individual light transmittance of each of the cells, and a set of stored in accordance with the backlight The plate illuminates the brightness and chromaticity distribution of the adjustment regions, and corresponds to a compensation device for compensating the uniformity of the transmitted light and chromaticity distribution of each of the adjustment regions, and the method comprises the following steps: b) receiving an image from an image The source includes a plurality of image data for instructing the image signals of the individual light transmittances of the cells, and c) weighting the image signals in the image data according to the corresponding adjustment regions, and weighting the compensation data according to the compensation data Obtaining compensation image data including a plurality of compensated image signals respectively corresponding to each of the unit cells; and d) determining, according to the compensated image signals, The individual light transmittance of the unit cell in the liquid crystal module; wherein, the adjustment regions are defined to achieve a uniform color chromaticity standard as a virtual basic color, and the virtual basic colors are red, green and blue basic colors. The tristimulus values are (X _rv , Y _rv , Z _rv ), (X _gv , Y _gb , Z _gv ), (X _bv , Y _bv , Z _bv ), and one of the crystal cells is measured. When the light transmittance of the liquid crystal valve is the largest, the three color red, green and blue three color stimulus values are (X _r , Y _r , Z _r ) _i , (X _g , Y _g , Z _{g i} , (X _b , Y _b , Z _b ) _i ; the compensated image signal (S' _r , S' _g , S' _b ) of the unit cell i in the step b) is the unit cell The inverse matrix of the tristimulus value matrix of i Tristimulus matrix with the virtual base color The conversion matrix (M _T ) _i obtained by the operation is applied to the original image signal (S _r , S _g , S _b ) _i . A method for uniformity compensation of a liquid crystal display having a non-uniform backlight, wherein the liquid crystal display comprises a set of non-uniform backlights, a set of cells on the light exit side of the backlight, including a plurality of cells with a changeable light transmittance, for display by a plurality a pixel-constituting screen, and the unit cell is divided into a plurality of liquid crystal modules of the adjustment area, a set of control means for controlling the individual light transmittance of each of the cells, and a set of stored in accordance with the backlight The plate illuminates the brightness and chromaticity distribution of the adjustment regions, and corresponds to a compensation device for compensating the uniformity of the transmitted light and chromaticity distribution of each of the adjustment regions, and the method comprises the following steps: b) receiving an image from an image The source includes a plurality of image data for instructing the image signals of the individual light transmittances of the cells, and c) weighting the image signals in the image data according to the corresponding adjustment regions, and weighting the compensation data according to the compensation data Obtaining compensation image data including a plurality of compensated image signals respectively corresponding to each of the unit cells; and d) determining, according to the compensated image signals, Cell permeation rate above the individual light in the liquid crystal module; wherein when the luminance of the regulatory region of such adjustment in the backlight of a region to adjust the value of k [alpha] _k, to be applied to such a unit cell of The original image signals of the unit cell i are (S _r , S _g , S _b ) _i , and the tristimulus value matrix of each of the adjustment regions is M _k , and the illumination coefficients of the adjustment region regions for the unit cell i are respectively λ _Ik , and defining the adjustment regions together can achieve one uniform chromaticity standard as a virtual basic color, the three-color stimuli value M _v of the red, green and blue basic colors of the virtual basic color, then the compensation of the unit cell i Image signal ) _i is The adjustment regions j, j+1, . . . , j+m are those having a predetermined influence on the unit cell i.